The federal government will investigate why infants born around Lake Superior have sometimes unhealthy levels of mercury in their blood, especially those along Minnesota's north shore.

The Environmental Protection Agency is expected to announce a $1.4 million grant to the Minnesota Department of Health to study mercury exposure among tribal communities and recreational anglers, both of whom rely on fish in their diet.

Details will be announced Thursday afternoon.

The research project follows a 2011 study that found one in 10 babies along Minnesota's North Shore are born with unhealthy levels of mercury in their bodies. The analysis of blood from 1,465 infants from Minnesota, Wisconsin and Michigan, was the first to prove that babies, who are most susceptible to the toxin, carried sometimes very high concentrations of it.

Those in Minnesota were more likely to have higher levels than their counterparts in Wisconsin and Michigan, most likely because their mothers ate more fish, the primary source of mercury in people. The toxin comes from coal fired plants around the world, and is deposited from air pollution. Over time, it accumulates in the bodies of fish.

Babies born in the summer months, when local fish consumption is highest, had more mercury than those born in winter, state officials said.

Mercury can affect the brain and nervous system development in fetuses and babies. At high levels, it's been shown to affect memory, attention and language. As a result, the EPA has established a health standard for women of childbearing age and infants of 5.8 millionths of a gram per liter of blood. Anything above that is considered unhealthy, though would not necessarily result in neurological problems.

Josephine Marcotty • 612-673-7394